The disclosure relates generally to processing of workpieces and more specifically to apparatus and methods for finishing internal surfaces of said workpieces.
Workpieces with internal cavities can require internal surface processing (roughening, smoothing, or introduction of compressive stresses) but current apparatus and methods do not form reliable and uniform application throughout the interior. Readily accessible surfaces (e.g., within the line of sight) may be addressed with machining, grinding, or a wide variety of abrasive media processes to improve the surface finish. Currently, these processes are most successful when applied to external surfaces and relatively short, straight internal passages with constant cross sections.
Non-line-of-sight internal passages with serpentine paths and irregularly shaped cavities are difficult or even impossible to effectively polish. Turbine engine components are one example of workpieces which contain such passages, and are subject to high cycle fatigue (HCF) and low cycle fatigue (LCF) service environments. The physics involved in additive manufacturing deposition processes for metal, polymer, and ceramic components results in a relatively rough, Ra 150 to Ra 1000 micro inches, as-built surface finish. An improved surface finish in the range of Ra 1 to Ra 125 micro inches can be required to avoid premature cracking and part failure.